Patent Application
20080079780
Further advantages of the exemplary embodiments will become apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale, wherein like reference numbers indicate like elements through the several views, and wherein:
As described in more detail below, embodiments of the disclosure relate to non-conventional substrates for providing micro-fluid ejection heads. Such non-conventional substrates, unlike conventional silicon substrates, may be provided in large format shapes to provide large arrays of fluid ejection actuators on a single substrate. Such large format shapes are particularly suited to providing page wide printers and other large format fluid ejection devices.
According to the disclosure, a substrate 10 (
With reference to
The valley 18 also has sloped side walls 22 having an angle 24 that provides a smooth radius (r) for electrical traces from the chip 14 to fluid ejection actuators 26 adjacent the peak 20 areas of the substrate 10. The angle 24 may range from about 45° to about 80° from an axis 28 substantially perpendicular to the surface 16. An equation for the smooth radius (r) is as follows:
r=D×√2
wherein r and D are as defined above. The smooth radius facilitates a continuous formation of thin film conductive layers, such as conductive trace 30 in the region extending between the valley 18 and the peak 20. The smooth radius is more adaptable than a sharper edge to thin film deposition methods and also may reduce residual stress build up in the conductive layers in the transition areas from the peak 20 along the sloped side walls 22 to the valley 18.
In order to provide a surface finish suitable for depositing fluid ejection devices and thin film conductive layers on the device surface 16 of the substrate 10, the device surface 16 of the substrate 10 may be polished to a fine finish and, if desired, coated with a planarizing layer. Polishing alone may be sufficient to provide a surface roughness of less than about 7.5 nanometers, which is generally a sufficiently smooth surface. If not, a layer of glass (for example boro-phospho-silicate glass BPSG) may be applied as by spinning or by chemical vapor depositing (CVD) onto the device surface 16 of the substrate 10. The techniques for applying the planarizing layer are well known in the semiconductor industry for coating silicon devices, but are not commonly used for coating non-conventional substrates such as substrate 10. According to an exemplary embodiment, there is a greater requirement for smoothness and planarity of the device surface 16 than there is for the sloped side walls 22 and valley floor 32 because of the deposition of fluid ejection devices 26 on the device surface 16, whereas only conductive traces 30 and contact pads 34 for the semiconductor chip 14 are provided on the sloped side walls 22 and valley floor 32, respectively,
After planarization of the device surface 16 of the substrate 10, a thermal conductive layer may be deposited in a fluid ejection actuator area of the substrate 10 and the fluid ejection actuators 26 and conductors therefor, for example, a thin film resistor layer and an anode and a cathode conductor layer, may be deposited adjacent to the thermal conductive layer. The thin film resistor layer and conductor layer may be patterned and etched using well known semiconductor fabrication techniques to provide a plurality of the fluid ejection actuators 26 on the device surface 16 of the substrate. Suitable semiconductor fabrication techniques include, but are not limited to, micro-fluid jet ejection of conductive inks, sputtering, chemical vapor deposition, and the like.
Formation of the conductive traces 30 on the sloped side walls 22 for connection to the fluid ejection actuators 26 may be achieved as by use of a photoresist masking layer that is photoimaged and developed to provide a mask for etching a blanket deposition of a conductive material for providing the conductive traces 30. If a positive photoresist material is used to pattern the conductive material, the conductive material is typically deposited prior to applying the photoresist material to the substrate 10. If a negative photoresist material is used, a thin film metal deposition step will typically follow patterning and developing the photoresist material.
The contact pads 34 for electrical connection to the semiconductor chip 14 may also be formed by conventional semiconductor processing techniques. Such contact pads 34 may be solder bumps or stud bumps made of a highly conductive material such as gold, gold/tin alloy, silver, or copper, and may be deposited to provide the contact pads 34 that are adjacent to the valley floor 32 as shown in
Once the fluid ejection actuators 26, conductors therefor, conductive traces, and contact pads 34 have been formed, the semiconductor chip 14 is attached to the contact pads 34, such as by a flip chip technique, to provide electrical flow communication between the semiconductor chip 14 and the fluid ejection actuators 26. In one embodiment, the semiconductor chip 14 provides fluid ejection actuator drivers 36, as illustrated in the electrical schematic of
In an alternate embodiment, a diode array containing diodes 38 may be used to provide a reduced number of chips 14 for activating the fluid ejection actuators 26 according to the electrical schematic of
After the chip 14 has been attached to the contact pads 34, an encapsulant material 44 may be deposited in the valley 18 to protect the electrical connections between the chip 14, the contact pads 34, and the conductive traces 30 and to planarize the substrate 10 as shown in
The ejection head 12 may also include one or more fluid supply slots 46 therein for providing fluid flow from a fluid reservoir to the fluid ejection actuators 26. Each fluid supply slot 46 may be machined or etched in the substrate 10 by conventional techniques such as deep reactive ion etching, chemical etching, sand blasting, laser drilling, sawing, and the like, to provide fluid flow communication from the fluid source to the device surface 16 of the substrate 10. The plurality of fluid ejection actuators 26 may be provided adjacent to one or both sides of the fluid supply slots 46.
In
In a further alternate embodiment, a substrate for the ejection head 12 or 48 may be selected from a metal such as tantalum, titanium aluminum, stainless steel, and the like, with a thin oxide layer deposited or formed adjacent to a device surface of the substrate. In this alternate embodiment, the substrate may provide both thermal conductivity properties as well as a ground plane for electrical connection between the actuators and/or driver device. In all other respects, the metal substrate may be configured in a manner set forth in this disclosure to provide control of the actuator devices deposited thereon.
It is contemplated, and will be apparent to those skilled in the art from the preceding description and the accompanying drawings that modifications and/or changes may be made in the embodiments of the disclosure. Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of exemplary embodiments only, not limiting thereto, and that the true spirit and scope of the present disclosure be determined by reference to the appended claims.
This application claims the benefit of U.S. Provisional Application No. 60/827,379, filed Sep. 28, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60827379 | Sep 2006 | US |
